Turns ratio v in to the primary v out measured in the secondary e. Utility to calculate tube amp estimated power transformer current requirements. Here you will find three example for typical operation of the 6l6gc tube they were provided by ge to make it easier for amp designers to use their tubesand gives us good info, too the 9th line effective load resistance, plate to plate gives the plate to plate load resistance or primary impedance of the ot for each of the three examples. Select an output transformer and a power tube from the builtin libraries. The tube bias calculator will calculate power tube bias values of plate current, dissipation and % of max dissipation using either measured voltage drop. Vacuum tube calculators basic theory using 21stcentury technology to design vacuum tube preamps, power amps, and power supplies system design a professional methodology for crafting a complete guitar amplifier. If you have an 8 ohm output transformer hooked up to an 8 ohm speaker, the transformer is seeing what it is looking for, if you hook the same transformer to a 16 ohm speaker it will have a 16 ohms load, the transformer is set up for 8 ohms and will run. We have been producing tube output transformers continuously for over 75 years, constantly improving and tweaking their performance.
By trying out several different sets of operating conditions in the computer i could eliminate hundreds of possibilities without playing with electricity. But since the output transformer was designed to load the current put out by 4 power tubes we need to make an adjustment on the speaker end to load 2 tubes properly. The following guidelines should be taken into account. A low value, under a few k indicates an internal short, and a dead transformer. First off, lets examine what an output transformer is and why someone would inquire about replacing it. Output transformerless otl is a type of vacuum tube audio power amplifier, which omits an output transformer for the purpose of greater linearity and fidelity. The next two are the dc resistance of the output transformer, followed by the impedance. A trio of software programs for the intrepid tubephile. A classic example of this is the lt700 audio transformer which can be used in the output stage of an amplifier to drive a loudspeaker. Realtime audio transformer emulation for virtual tube amplifiers. Tube bias calculator rob robinettes car and tube amp website. Are you looking for the best transformer calculator software for your next project.
Tubes do not affect impenitence, speaker load does. The two output trannys are rotated 90deg to the power mains tranny to avoid picking up induced hum from the mains tranny external magnetic field. Tube amp power transformer current draw calculator javascript must be enabled in order for the calculations to work. The one thing im stuck on is the output transformer, according to the datasheet i need to get a 35004000 ohm transformer with a 4 ohm output to power a car speaker i have. We offer transformer covers for the output and mains transformers and chokes of your diy tube amp. Bear in mind that the 5f6a was intended to be used clean as a bass amp rather than an overdriven guitar amp. Audio transformer is the primary part of a tube amplifier which generates an electromagnetic field. If a tube arcs internally, it can create a high voltage. Single ended output transformer calculating spreadsheet. From the tube data books, you determine that a pair of 6l6s will put 4050w in class ab push pull into a 4400 ohm plate to plate impedance. Pushpull output transformer spreadsheet calculator with pdf. Please visit my tube amplifier forum heres the place you can go to ask tube amplifier questions. Feb 02, 2017 testing an unknown output transformer on a speaker i recently acquired. Conventional vacuum tube amplifier designs rely upon an output transformer to couple the amplifiers output stage to the loudspeaker.
It is important to note, however, that these solutions are best only for those experts who have knowledge and experience with assembly transformers. I am often asked how upgrading an amplifiers transformers will improve tone. This means that, with the transformer in question having a 25 turns ratio, the load presented to the tube would be 252 x 50 31. Output amplifier consists of a 6p1p output tube and output transformer fig. Many pushpull amps designed to run 4 power tubes can be run with 2 power tubes to cut the output power in half. For amps with cathode bias resistors you can simply measure their voltage drop and use the tube dissipation using cathode resistor voltage drop calculator. The sense of a tube amp opening up and producing a singing overdriven note is certainly a function of the transformer compressing and putting its signature on things. The 50s amps that are most renowned for having this smaller ot are the tweed 5e5 pro, 5f4 super, and 5e7 bandmaster prior to this, the ots used for two 6l6s were. Amp diy adventures in amplification gear diy amps howtos.
Understanding your output transformer part one by mark baier. Because of this, the cost of the output transformer often accounts for a very big part of the total cost of a tube amplifier. Output trannys contribute most of the distortion in a valve amp and have a limited bandwidth. All covers are made in germany and sold ex factory. There are several things that are important in getting an output transformer made. Looking through all of my scavenged transformers i cant find a single one in the thousands of ohms, most are a few hundred and lower. Audio transformers are designed for use in audio amplifier applications for. If you would like to simply calculate number of turns and other aspects of your output transformer for a pushpull tube guitar amp or a home hifi tube amp, dont miss out on this tried and tested method which is an easy to use excel spreadsheet that automatically calculates the transformer windings according to your needs. System design a professional methodology for crafting a complete guitar amplifier. Its a simple enough question, but the answer is a little complex. We know that for a transformer, the ratio between the number of coil turns on the primary winding n p to the number of coil turns on the secondary winding n s is called the turns ratio.
If you would like to simply calculate number of turns and other aspects of your output transformer for a single ended tube guitar amp or a hifi home tube amp, dont miss out on this tried and tested method which is an easy to use excel spreadsheet which automatically calculates a transformer according to your needs. Why and how to replace your amplifiers output transformer. Some designs sound better with a small output transformer. The core is what really makes this device what it is. A low reading here indicates a short to the transformer core again, dead transformer. If you used an 8 ohm tap, a 4 ohm tap will have about 2. How to calculate the output transformer impedance of an opt with unknown values. Building a tube amp, how to calculate output transformer. Ttgcfb4000pp tube output cfb transformer 4kohm cathode feedback pushpull.
When you adjust these you see the voltages change on the schematic. In general it would be possible to reduce the nonlinearities in an amplifier below any desired value by the application of a sufficient amount of feedback. Single ended output transformer calculating spreadsheet with. In this video, i discuss the design and function of power transformers pt, primarily those utilized in amplifiers. Moreover, it is extremely difficult and therefore very expensive to make a good output transformer. More than 80% of our transformers manufactured is for this market and bring over 70 years transformer manufacturing expertise to our product. The objective of this project is to develop an output transformer for singleended tube amplifiers with. If you need assistance with circuit protection devices such as fuses or breakers, or wire sizing, please consult a licensed electrical contractor or electrician in your area who will be familiar with state and local codes. My recommended bias measurement method is the output transformer resistance method. Jan 31, 2014 in this video, i discuss the design and function of power transformers pt, primarily those utilized in amplifiers. It was suggested that you could put an 8 ohm load on a 16 ohm 5k primary transformer to get a 2. If you want to see tube amplifiers built by customers, visit our customer tube amp gallery.
Those of us who are in search of perfection in audio amplifiers must often have looked askance at the output transformer. First off, lets examine what an output transformer is and. Topics such as winding ratio, output voltage, current limitations, and mounting. Tube amp output transformer impedance matching headphone. The crack has no output transformers and as a result of its particular design, it has a high output impedance 120 ohm. Audio output transformers are heavily used in a vacuum tube and some. Sep 27, 2014 tcj pushpull calculator has but a single purpose. Prices are generally extortionate, though they do sell a good 25w output transformer online. Calculating output transformer impedance sarris custom. Pushpull output transformer spreadsheet calculator with. Amplifiers without the output transformer therefore produce cleaner, less distorted sound. Working with tube amps you may need to calculate the output transformer impedance especially when we have an old transformer or a transformer with unknown values.
An excellent site in the netherlands, selling a good range of valve amp related components. The cost of a tube amplifier mostly consists of the cost of an output transformer and tubes that is usually a factor limiting the sound quality. Wide band output transformers with third winding for nfb exclusive use, which can make stabilized nfb. Tube output transformers, which ones are really good. Optional rload in ohms typically the output transformer primary impedance. The free shipping option allows tubedepot to choose the most appropriate carrier and service. Finally, test for the resistance from primary to secondary.
So we apply an ac voltage to the primary of the transformer and we measure the output voltage to the secondary. That can cause arcing inside the output tubes and, of course insulation breakdown in the transformer. You measure the output transformer s voltage drop and resistance to calculate the bias current. Professionals with experience in transformer assemblies use the computer program to calculate the number of coils and wire thickness. Optional rload in ohms typically the output transformer primary impedance only considered when pp pushpull is selected number of tubes power tubes pre amp tubes. Output transformers in tube amplifier designs are typically used to lower the amplifiers output impedance and to make them more universally compatible with many headphones. Brainstock video production our diy amp, studio, gear blog. Hammond manufactures direct replacement transformers for popular tube amps from fender, marshall, vox, ampeg, orange, and yorkville traynor. I just got this response when i asked someone about swapping 6v6 and 6l6 power tubes. Testing an unknown output transformer on a speaker i recently acquired. Apr 30, 2010 the output transformer is the heart of a valve amplifier.
But since the output transformer was designed to load the current put out by 4 power tubes we need to. This method is more dangerous because when your meter probe. Tamura corporation audio transformers for tube amp. You can change the tube current, and the cathode resistor will change, or change the cathode resistor and the tube current will change.
Tube amp transformers tube amp parts, guitar amp parts. Understanding your output transformer part one by mark. Some folks will judge an amp by the size of the output transformer but this is matter of taste. Circuit of tube amplifier device the output transformer is an important part of the amplifier requiring a thorough parameter determination. Calculating output transformer impedance sarris custom tube. Assembly manual schematic parts list tubes and applications design simulations. This might give you some interesting ideas for your own projects. Projects, mods, transformer diagrams, photos, sound clips. The cathode resistor in a typical triode preamp is bypassed with a large capacitor to eliminate a form of negative.
This is necessary to get an efficient transfer of the audio signal to the speaker. Secondaries should have multiples of the voltage youre putting on the tap you chose. You measure the output transformers voltage drop and resistance to calculate the bias current. The function of the audio output transformer is to transform the high impedance of the output tube to match the much lower impedance of the speaker.
Generally speaking the larger the output transformer the more low end and clean headroom in the power stage the amp will have. Output transformer primary impedance the gear page. How amps work rob robinettes car and tube amp website. You can also measure the actual plate current by shunting the output transformer with a multimeter in the dc milliamps mode and use the tube dissipation using plate current calculator. Tube output transformer 5kohm 2x6as7g 2x6ns pushpull or similar. Calculate the nominal impedance of the loudspeaker required for maximum. The output transformer as an impedance matching device, works on the principal of reflected load. As an example, you might want to design an output transformer for a single pair of 6l6 output tubes. Iif you would like to calculate and wind your own single ended and push pull output transformers for guitar amps and home hifi amplifiers, ive. There are hundreds of pages of tube amp information on my library page. I volunteered to put a 4 ohm load on my amplifier and re run the tests.
The more modern approach is to use a direct coupled cathode follower to drive the output tube grid so it allowed triode to make a similar of power in class a2 as a pentode or tetrode with the same idle power. The halfprimaries of the output transformer should have identical voltages on them. To separate the high voltage and match the speaker impendance with the tube impendance we. I brought the tubes over to a friend that had a tube tester and they work as they should. Usually tube arcing does not cause permanent damage to the tube, but it is possible. Jun 08, 2014 the way i understand things is that the transformer doesnt have an own impedance, rather it reflects the load impedance based on the square of its turns ratio and presents that to the tube. Whether you are into the clean, free spirited single ended tube output or high efficiency, high power, pushpull audio, we have the output transformer for you. The tube amp library of information click the link above for tube amp info, schematics, board building information. There is really one circuit this thing was made for that is a cathode follower. Instead, otls use one of two primary methods for output stage coupling. The wattage output in an amplifier may vary from application to application due to many variables such as tube types, solid state vs. The way i understand things is that the transformer doesnt have an own impedance, rather it reflects the load impedance based on the square of its turns ratio and presents that to the tube. Do a similar test on the secondaries look for open windings, or shorts to the core.
Nov 18, 20 the sense of a tube amp opening up and producing a singing overdriven note is certainly a function of the transformer compressing and putting its signature on things. Vacuum tube calculators basic theory using 21stcentury technology to design vacuum tube preamps, power amps, and power supplies system design a professional methodology for crafting a. Running at full power and no load will create very high voltages across the output transformer primary. The output transformer is the heart of a valve amplifier. Transformer calculator kva calculator full load amps calculator. Audio transformer and impedance matching transformer.
Hammond puts a century of experience into manufacturing high quality magnetics for tube applications like hifi audio and guitar amplifiers. In a nutshell, this program is a virtual workbench for singleended tube amplifier output stage design. Next select the type of bias fixed or cathode and power supply dc or ac. Calculation of output transformers the output transformer is probably the most expensive part in the amplifier and something you have to live with if you like classic tube amplification. Basic theory using 21stcentury technology to design vacuum tube preamps, power amps, and power supplies. To get rid of flub, coupling caps are best reduced in value. Tube bias calculator rob robinettes car and tube amp. To separate the high voltage and match the speaker impendance with the tube impendance we need audio grade output transformer.
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